Re: Using Datalog as a common semantics for SQL/RIF-based approaches?

> On Sun, Jul 18, 2010 at 11:39 AM, Harry Halpin <hhalpin@w3.org> wrote:
>> In our specification, it will be important to both specify exactly what
>> needs to be implemented that users can expect to be portable and have
>> extensibility mechanisms that work in a principled manner.
>>
>> The options that we've seen so far both seem to have problems. SPARQL
>> constructs are not expressive enough, but then RIF is likely too
>> expressive, and it would be doubtful if we could convince implementers
>> to
>> implement all of RIF just to map relational data to RDF. Likewise, SQL
>> is
>> a large language itself that is implemented differently in the details
>> across vendors, so we'd have to specify exactly what part of SQL we
>> thought must be implemented. How to do so?
>>
>> I'm intrigued that we could use another option - specify a common
>> semantics using Datalog that then could be expressed using some subset
>> of
>> RIF and SQL. In fact, ideally the language could use Datalog to
>> translate
>> between the subset of RIF and SQL and vice-versa. Then we could also
>> take
>> advantage of SQL's power and implementation exprience while having the
>> nice extensibility mechanisms of RIF.
>
> I like this approach!
>
> The fragment of Datalog that we need to use for the mapping language
> has a simple syntax and a semantics that can be easily understood, so
> it is a good alternative.

Glad you like it.

Can you send a few good references about this fragment to the list? Either
papers (ideal) or even references from journal/textbooks?  For those of us
who are not familiar with this work, we need something more detailed than
examples in order to figure out the exact fragment that we could map to
RIF.

If I can get these references or this information out of the meeting
tomorrow, I'm happy to try to get Harold Boley, Michael Kifer to work out
the semantics of mapping that fragment to RIF, and we'd probably need to
have a discussion with Sandro (W3C RIF contact) on introducing RIF to this
WG (as I would assume that most of us aren't familiar with it).

The other topic would be to see if this SQL fragment would be a good
starting point for the SQL-based approach as well.

>
> We have been working with Juan in the mapping language and also in a
> comparison with Eric's default mapping, that we would like to present
> to the group tomorrow. Hopefully tonight you will be able to find this
> material here:
>
> http://www.w3.org/2001/sw/rdb2rdf/wiki/Database-Instance-Only_and_Database-Instances-and-Schema_Mapping
>
> All the best,
>
> Marcelo
>
>

Received on Monday, 19 July 2010 14:42:39 UTC